U.S. patent application number 13/138637 was filed with the patent office on 2012-01-05 for catalyst separation system.
Invention is credited to Yasuhiro Onishi, Eiichi Yamada.
Application Number | 20120003127 13/138637 |
Document ID | / |
Family ID | 42739412 |
Filed Date | 2012-01-05 |
United States Patent
Application |
20120003127 |
Kind Code |
A1 |
Onishi; Yasuhiro ; et
al. |
January 5, 2012 |
CATALYST SEPARATION SYSTEM
Abstract
A catalyst separation system is provided with: a reactor where
hydrocarbons are synthesized by a chemical reaction of a synthesis
gas including carbon monoxide gas and hydrogen gas as main
components, and a catalyst slurry having solid catalyst particles
suspended in a liquid; filters which separate the hydrocarbons and
the catalyst slurry; and a gas-liquid separator which separates the
liquid hydrocarbons flowing out of the filter into gas hydrocarbons
and liquid hydrocarbons.
Inventors: |
Onishi; Yasuhiro; (Tokyo,
JP) ; Yamada; Eiichi; (Yokohama-shi, JP) |
Family ID: |
42739412 |
Appl. No.: |
13/138637 |
Filed: |
March 1, 2010 |
PCT Filed: |
March 1, 2010 |
PCT NO: |
PCT/JP2010/001364 |
371 Date: |
September 13, 2011 |
Current U.S.
Class: |
422/187 |
Current CPC
Class: |
C10G 31/09 20130101;
B01J 8/006 20130101; B01J 8/22 20130101; B01J 2219/00006 20130101;
C10G 2/342 20130101 |
Class at
Publication: |
422/187 |
International
Class: |
B01J 19/00 20060101
B01J019/00 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 19, 2009 |
JP |
2009-068829 |
Claims
1. A catalyst separation system comprising: a reactor where
hydrocarbons are synthesized by a chemical reaction of a synthesis
gas including carbon monoxide gas and hydrogen gas as main
components, and a catalyst slurry having solid catalyst particles
suspended in a liquid; filters which separate the hydrocarbons and
the catalyst slurry; and a gas-liquid separator which separates the
liquid hydrocarbons flowing out of the filter into gas hydrocarbons
and liquid hydrocarbons.
2. The catalyst separation system according to claim 1, wherein the
chemical reaction is a Fischer-Tropsch synthesis reaction.
3. The catalyst separation system according to claim 1 or 2,
wherein the gas-liquid separator has a plurality of branch pipes
which extend from the filters, and a collecting pipe which collects
a fluid which flows through the branch pipes, and has a larger
diameter than the branch pipes.
4. The catalyst separation system according to claim 3, wherein the
collecting pipe is a ring-shaped header.
5. The catalyst separation system according to claim 4, wherein the
header is arranged above the filters so that the center thereof is
made to coincide with the center of the reactor which houses the
filters.
6. The catalyst separation system according to claim 4 or 5,
wherein a liquid flowing line through which the liquid hydrocarbons
separated within the ring-shaped header are transferred, and a gas
flowing line through which the gas hydrocarbons separated within
the ring-shaped header are transferred are connected to the
ring-shaped header.
Description
TECHNICAL FIELD
[0001] The present invention relates to a catalyst separation
system which separates liquid hydrocarbons from a catalyst
slurry.
[0002] Priority is claimed on Japanese Patent Application No.
2009-68829, filed Mar. 19, 2009, the content of which is
incorporated herein by reference.
BACKGROUND ART
[0003] As one of the methods for synthesizing liquid fuels from
natural gas, a GTL (Gas to Liquid: liquid fuel synthesis) technique
of reforming natural gas to produce a synthesis gas including
carbon monoxide gas (CO) and hydrogen gas (H.sub.2) as main
components, synthesizing hydrocarbons using a catalyst with this
synthesis gas as a source gas by the Fischer-Tropsch synthesis
reaction (hereinafter referred to as "FT synthesis reaction"), and
further hydrogenating and refining the hydrocarbons to produce
liquid fuel products, such as naphtha (raw gasoline), kerosene, gas
oil, and wax, has recently been developed.
[0004] The liquid hydrocarbons synthesized by the FT synthesis
reaction are separated from the catalyst slurry, which has solid
catalyst particles suspended in the liquid hydrocarbons, before
being transferred to a refining process in the subsequent process
where the hydrocarbons are converted into naphtha, kerosene, etc.
Conventionally, as a device to separate liquid hydrocarbons from a
catalyst slurry, a method which passes the hydrocarbons through
filters is suggested, as described in, for example, Patent Document
1.
CITATION LIST
Patent Literature
[0005] [Patent Document 1] Specification of US Patent Application
Laid-Open Publication No. 2005-0080149
SUMMARY OF THE INVENTION
Technical Problem
[0006] When liquid hydrocarbons are separated from the catalyst
slurry as described above, gas hydrocarbons, etc. may be mixed into
the liquid hydrocarbons filtered by the filters simply by passing
the hydrocarbons through the filters. This is because gas
hydrocarbons pass through the filters directly or a portion of the
liquid hydrocarbons evaporates as the pressure on the downstream of
the filters is reduced. When the hydrocarbons are transferred to
the downstream side in a mixed vapor-liquid phase in this way,
pressure loss in pipes increases as the volume expands during
transfer, and the flow volume of hydrocarbons decreases.
[0007] The present invention was made in view of such a problem,
and the object thereof is to provide a catalyst separation system
capable of minimizing a pressure loss, thereby securing a
predetermined flow volume, when the liquid hydrocarbons synthesized
by the FT synthesis reaction are separated from the catalyst slurry
and transferred downstream.
Solution to the Problem
[0008] A catalyst separation system of the present invention
includes: a reactor where hydrocarbons are synthesized by a
chemical reaction of a synthesis gas including carbon monoxide gas
and hydrogen gas as main components, and a catalyst slurry having
solid catalyst particles suspended in a liquid; filters which
separate the hydrocarbons and the catalyst slurry; and a gas-liquid
separator which separates the liquid hydrocarbons flowing out of
the filters into gas hydrocarbons and liquid hydrocarbons.
[0009] Additionally, in the above catalyst separation system, the
chemical reaction may be a Fischer-Tropsch synthesis reaction.
[0010] According to this invention, hydrocarbons are synthesized by
the chemical reaction of the synthesis gas and the catalyst slurry
within the reactor. The catalyst slurry is separated from the
synthesized hydrocarbons by the filters, and transferred to the
gas-liquid separator downstream. Although gas hydrocarbons are also
included in the hydrocarbons from which the catalyst slurry has
been separated by the filters, the hydrocarbons are separated into
gas hydrocarbons and liquid hydrocarbons when being transferred to
the gas-liquid separator. Since the hydrocarbons are separated into
gas and liquid in this way, the gas hydrocarbons and the liquid
hydrocarbons can be transferred separately when being further
transferred downstream from the gas-liquid separator. Accordingly,
pressure loss within a transfer line can be minimized.
[0011] Additionally, in the above catalyst separation system, the
gas-liquid separator may have a plurality of branch pipes which
extend from the filters, and a collecting pipe which collects a
fluid which flows through the branch pipes, and has a larger
diameter than the branch pipes.
[0012] According to this invention, the liquid hydrocarbons
separated by the filters are transferred to the collecting pipe
from the branch pipes in a state where the gas hydrocarbons are
included. Since the collecting pipe has a larger diameter than the
branch pipes, vapor liquid separation will occur even in a portion
during transfer to the collecting pipe from the branch pipes, as
well as in the collecting pipe. As a result, the gas-liquid
separation time can be shortened.
[0013] Additionally, in the above catalyst separation system, the
collecting pipe may be a ring-shaped header.
[0014] According to this invention, when the fluid of the
hydrocarbons is transferred to the header from the plurality of
branch pipes, the fluid can be transferred to the header under the
same conditions, and a smooth flow of the fluid within the header
can be achieved.
[0015] Additionally, in the above catalyst separation system, the
ring-shaped header may be arranged above the filters so that the
center thereof is made to coincide with the center of the reactor
which houses the filters.
[0016] According to this invention, since the ring-shaped header is
arranged so that the center thereof is made to coincide with the
center of the reactor, an exclusive space for the header and
container can be made small, and an apparatus can be made compact.
Additionally, since the liquid hydrocarbons including gas
hydrocarbons separated by the filters are transferred to the
ring-shaped header via the branch pipes, smooth transfer of the
liquid hydrocarbons is allowed while performing vapor liquid
separation.
[0017] Additionally, in the above catalyst separation system, a
liquid flowing line through which the liquid hydrocarbons within
the ring-shaped header are transferred, and a gas flowing line
through which the gas hydrocarbons within the ring-shaped header
are transferred may be connected to the ring-shaped header.
[0018] According to this invention, among the hydrocarbons
separated by the ring-shaped header, the liquid hydrocarbons are
transferred by the liquid flowing line, and the gas hydrocarbons
are transferred by the gas flowing line. As such, the gas
hydrocarbons and the liquid hydrocarbons which have been subjected
to vapor liquid separation can be separately transferred
downstream.
Advantageous Effects of Invention
[0019] According to the catalyst separation system of the present
invention, when liquid hydrocarbons synthesized by the FT synthesis
reaction are separated from a catalyst slurry and transferred
downstream, the hydrocarbons can be first separated into gas
hydrocarbons and liquid hydrocarbons, and transferred separately.
Thus, it is possible to minimize pressure loss in a transfer path.
As a result, a predetermined flow volume can be secured.
BRIEF DESCRIPTION OF THE DRAWINGS
[0020] FIG. 1 is a schematic diagram showing the overall
configuration of a liquid fuel synthesizing system including a
catalyst separation system of a first embodiment of the present
invention.
[0021] FIG. 2 is a schematic diagram showing the overall
configuration of the catalyst separation system of the first
embodiment of the present invention.
[0022] FIG. 3 is a schematic diagram showing the overall
configuration of a catalyst separation system of a second
embodiment of the present invention.
DESCRIPTION OF EMBODIMENTS
First Embodiment
[0023] Hereinafter, a first embodiment of a catalyst separation
system according to the present invention will be described with
reference to FIGS. 1 to 3.
[0024] First, the overall configuration of a liquid fuel
synthesizing system 1 including a catalyst separation system 81 of
the present invention will be described with reference to FIG.
1.
[0025] As shown in FIG. 1, the liquid fuel synthesizing system 1 is
a plant facility which carries out the GTL process which converts a
hydrocarbon feedstock, such as natural gas, into liquid fuels. This
liquid fuel synthesizing system 1 includes a synthesis gas
production unit 3, an FT synthesis unit 5, and an upgrading unit 7.
The synthesis gas production unit 3 reforms a natural gas, which is
a hydrocarbon feedstock, to produce a synthesis gas including a
carbon monoxide gas and a hydrogen gas. The FT synthesis unit 5
produces liquid hydrocarbons from the produced synthesis gas by the
FT synthesis reaction. The upgrading unit 7 hydrogenates and
refines the liquid hydrocarbons produced by the FT synthesis
reaction to produce liquid fuel products (naphtha, kerosene, gas
oil, wax, etc.). Hereinafter, components of each of these units
will be described.
[0026] First, the synthesis gas production unit 3 will be
described. The synthesis gas production unit 3 mainly includes, for
example, a desulfurizing reactor 10, a reformer 12, a waste heat
boiler 14, vapor-liquid separators 16 and 18, a CO.sub.2 removal
unit 20, and a hydrogen separator 26.
[0027] The desulfurizing reactor 10 is composed of a
hydrodesulferizer, etc., and removes sulfur components from a
natural gas as a feedstock. The reformer 12 reforms the natural gas
supplied from the desulfurizing reactor 10, to produce a synthesis
gas including a carbon monoxide gas (CO) and a hydrogen gas
(H.sub.2) as the main components. The waste heat boiler 14 recovers
waste heat of the synthesis gas produced in the reformer 12, to
produce high-pressure steam. The vapor-liquid separator 16
separates the water heated by the heat exchange with the synthesis
gas in the waste heat boiler 14 into a vapor (high-pressure steam)
and a liquid. The vapor-liquid separator 18 removes condensate from
the synthesis gas cooled down in the waste heat boiler 14, and
supplies a gas to the CO.sub.2 removal unit 20. The CO.sub.2
removal unit 20 has an absorption tower 22 which removes carbon
dioxide gas by using an absorbent from the synthesis gas supplied
from the vapor-liquid separator 18, and a regeneration tower 24
which desorbs the carbon dioxide gas and regenerates the absorbent
including the carbon dioxide gas. The hydrogen separator 26
separates a portion of the hydrogen gas included in the synthesis
gas, the carbon dioxide gas of which has been separated by the
CO.sub.2 removal unit 20. It is to be noted herein that the above
CO.sub.2 removal unit 20 may not be provided depending on
circumstances.
[0028] Among them, the reformer 12 reforms a natural gas by using a
carbon dioxide and a steam to produce a high-temperature synthesis
gas including a carbon monoxide gas and a hydrogen gas as the main
components, by a steam and carbon-dioxide-gas reforming method
expressed by the following chemical reaction formulas (1) and (2).
In addition, the reforming method in this reformer 12 is not
limited to the example of the above steam and carbon-dioxide-gas
reforming method. For example, a steam reforming method, a partial
oxidation reforming method (POX) using oxygen, an autothermal
reforming method (ATR) that is a combination of the partial
oxidation method and the steam reforming method, a
carbon-dioxide-gas reforming method, and the like can also be
utilized.
CH.sub.4+H.sub.2O.fwdarw.CO+3H.sub.2 (1)
CH.sub.4+CO.sub.2.fwdarw.2CO+2H.sub.2 (2)
[0029] Additionally, the hydrogen separator 26 is provided on a
line branching from a pipe which connects the CO.sub.2 removal unit
20 or vapor-liquid separator 18 with the bubble column reactor 30.
This hydrogen separator 26 can be composed of, for example, a
hydrogen PSA (Pressure Swing Adsorption) device which performs
adsorption and desorption of hydrogen by using a pressure
difference. This hydrogen PSA device has adsorbents (zeolitic
adsorbent, activated carbon, alumina, silica gel, etc.) within a
plurality of adsorption towers (not shown) which are arranged in
parallel. By sequentially repeating processes including
pressurizing, adsorption, desorption (pressure reduction), and
purging of hydrogen in each of the adsorption towers, a high-purity
(for example, about 99.999%) hydrogen gas separated from the
synthesis gas can be continuously supplied to a reactor.
[0030] In addition, the hydrogen gas separating method in the
hydrogen separator 26 is not limited to the example of the pressure
swing adsorption method as in the above hydrogen PSA device. For
example, the method may be a hydrogen storing alloy adsorption
method, a membrane separation method, or a combination thereof.
[0031] The hydrogen storing alloy method is, for example, a
technique of separating hydrogen gas using a hydrogen storing alloy
(TiFe, LaNi.sub.5, TiFe.sub.0.7-0.9, Mn.sub.0.3-0.1, TiMn.sub.1.5,
etc.) having a property which adsorbs or emits hydrogen by being
cooled or heated. By providing a plurality of adsorption towers in
which a hydrogen storing alloy is contained, and alternately
repeating, in each of the adsorption towers, adsorption of hydrogen
by cooling of the hydrogen storing alloy and emission of hydrogen
by heating of the hydrogen storing alloy, hydrogen gas in the
synthesis gas can be separated and recovered.
[0032] Additionally, the membrane separation method is a technique
of separating hydrogen gas having excellent membrane permeability
out of a mixed gas, using a membrane made of a polymeric material,
such as aromatic polyimide. Since this membrane separation method
is not accompanied with a phase change, less energy for running is
required, and the running cost is low. Additionally, since the
structure of a membrane separation device is simple and compact,
low facility cost is required and the required area of the facility
is also less. Moreover, since there is no driving device in a
separation membrane, and a stable running range is wide, there is
an advantage in that maintenance and management are easy.
[0033] Next, the FT synthesis unit 5 will be described. The FT
synthesis unit 5 mainly includes, for example, the bubble column
reactor 30, a vapor-liquid separator 34, a separator 36, a
vapor-liquid separator 38, and a first fractionator 40.
[0034] The bubble column reactor 30, which is an example of a
reactor which synthesizes synthesis gas into liquid hydrocarbons,
functions as an FT synthesis reactor which synthesizes liquid
hydrocarbons from synthesis gas by the FT synthesis reaction. The
bubble column reactor 30 is composed of, for example, a bubble
column slurry bed type reactor in which a catalyst slurry
consisting mainly of catalyst particles and medium oil is contained
inside a tower reactor. This bubble column reactor 30 produces gas
or liquid hydrocarbons from the synthesis gas by the FT synthesis.
In detail, in this bubble column reactor 30, the synthesis gas that
is a source gas is supplied as bubbles from a spager at the bottom
of the bubble column reactor 30, and passes through the catalyst
slurry, and in a suspended state, a hydrogen gas and a carbon
monoxide gas undergo a synthesis reaction, as shown in the
following chemical reaction formula (3).
2nH.sub.2+nCO.fwdarw.CH.sub.2n+nH.sub.2O (3)
[0035] Since this FT synthesis reaction is an exothermic reaction,
the bubble column reactor 30, which is a heat exchanger type
reactor within which the heat transfer pipe 32 is disposed, is
adapted such that, for example, water (BFW: Boiler Feed Water) is
supplied as a coolant so that the reaction heat of the above FT
synthesis reaction can be recovered as a medium-pressure steam by
the heat exchange between the slurry and the water.
[0036] The vapor-liquid separator 34 separates the water
transferred and heated through the heat transfer pipe 32 disposed
within the bubble column reactor 30 into a steam (medium-pressure
steam) and a liquid. The separator 36, which is an example of a
filter which separates the catalyst slurry and the liquid
hydrocarbons, is arranged inside the bubble column reactor 30. The
vapor-liquid separator 38 is connected to the top of the bubble
column reactor 30 to cool down unreacted synthesis gas and gas
hydrocarbon products. The first fractionator 40 distills the liquid
hydrocarbons supplied via the separator 36 within the bubble column
reactor 30 and the vapor-liquid separator 38, and fractionally
distills the liquid hydrocarbons into individual fractions
according to boiling points.
[0037] Finally, the upgrading unit 7 will be described. The
upgrading unit 7 includes, for example, a wax fraction
hydrocracking reactor 50, a middle distillate hydrotreating reactor
52, a naphtha fraction hydrotreating reactor 54, vapor-liquid
separators 56, 58, and 60, a second fractionator 70, and a naphtha
stabilizer 72. The wax fraction hydrocracking reactor 50 is
connected to the bottom of the first fractionator 40. The middle
distillate hydrotreating reactor 52 is connected to a middle part
of the first fractionator 40. The naphtha fraction hydrotreating
reactor 54 is connected to the top of the first fractionator 40.
The vapor-liquid separators 56, 58 and 60 are provided so as to
correspond to the hydrogenation reactors 50, 52 and 54,
respectively. The second fractionator 70 separates and refines the
liquid hydrocarbons supplied from the vapor-liquid separators 56
and 58 according to boiling points. The naphtha stabilizer 72
distills liquid hydrocarbons of a naphtha fraction supplied from
the vapor-liquid separator 60 and the second fractionator 70, to
discharge components lighter than butane as flare gas, and to
recover components having a carbon number of five or more as a
naphtha product.
[0038] Next, a process (GTL process) of synthesizing liquid fuels
from a natural gas by the liquid fuel synthesizing system 1
configured as above will be described.
[0039] A natural gas (the main component of which is CH.sub.4) as a
hydrocarbon feedstock is supplied to the liquid fuel synthesizing
system 1 from an external natural gas supply source (not shown),
such as a natural gas field or a natural gas plant. The above
synthesis gas production unit 3 reforms this natural gas to produce
a synthesis gas (mixed gas including a carbon monoxide gas and a
hydrogen gas as main components).
[0040] Specifically, first, the above natural gas is supplied to
the desulfurizing reactor 10 along with the hydrogen gas separated
by the hydrogen separator 26. The desulfurizing reactor 10
hydrogenates and desulfurizes sulfur components included in the
natural gas using the hydrogen gas, for example, with a ZnO
catalyst. By desulfurizing the natural gas in advance in this way,
it is possible to prevent deactivation of catalysts used in the
reformer 12, the bubble column reactor 30, etc. by sulfur
components.
[0041] The natural gas (may also contain a carbon dioxide)
desulfurized in this way is supplied to the reformer 12 after the
carbon dioxide (CO.sub.2) gas supplied from a carbon-dioxide supply
source (not shown) and the steam generated in the waste heat boiler
14 are mixed therewith. The reformer 12 reforms a natural gas by
using a carbon dioxide and a steam to produce a high-temperature
synthesis gas including a carbon monoxide gas and a hydrogen gas as
the main components, by a the above steam and carbon-dioxide-gas
reforming method. At this time, the reformer 12 is supplied with,
for example, a fuel gas for a burner disposed in the reformer 12
and air, and the reaction heat required for the above steam and
CO.sub.2 reforming reaction that is an endothermic reaction is
provided with the heat of combustion of the fuel gas in the
burner.
[0042] The high-temperature synthesis gas (for example, 900.degree.
C., 2.0 MPaG) produced in the reformer 12 in this way is supplied
to the waste heat boiler 14, and is cooled down by the heat
exchange with the water which flows through the waste heat boiler
14 (for example, 400.degree. C.), thus the waste heat is recovered.
At this time, the water heated by the synthesis gas in the waste
heat boiler 14 is supplied to the vapor-liquid separator 16. From
this vapor-liquid separator 16, a gas component is supplied to the
reformer 12 or other external devices as a high-pressure steam (for
example, 3.4 to 10.0 MPaG), and water as a liquid component is
returned to the waste heat boiler 14.
[0043] Meanwhile, the synthesis gas cooled down in the waste heat
boiler 14 is supplied to the absorption tower 22 of the CO.sub.2
removal unit 20, or the bubble column reactor 30, after a
condensate is separated and removed from the synthesis gas in the
vapor-liquid separator 18. The absorption tower 22 absorbs a carbon
dioxide gas included in the synthesis gas into the retained
absorbent, to separate the carbon dioxide gas from the synthesis
gas. The absorbent including the carbon dioxide gas within this
absorption tower 22 is introduced into the regeneration tower 24,
the absorbent including the carbon dioxide gas is heated and
subjected to stripping treatment with, for example, a steam, and
the resulting desorbed carbon dioxide gas is recycled sent to the
reformer 12 from the regeneration tower 24, and is reused for the
above reforming reaction.
[0044] The synthesis gas produced in the synthesis gas production
unit 3 in this way is supplied to the bubble column reactor 30 of
the above FT synthesis unit 5. At this time, the composition ratio
of the synthesis gas supplied to the bubble column reactor 30 is
adjusted to a composition ratio (for example, H.sub.2:CO=2:1 (molar
ratio)) suitable for the FT synthesis reaction. In addition, the
pressure of the synthesis gas supplied to the bubble column reactor
30 is raised to a pressure (for example, about 3.6 MPaG) suitable
for the FT synthesis reaction by a compressor (not shown) provided
in a pipe which connects the CO.sub.2 removal unit 20 with the
bubble column reactor 30.
[0045] Additionally, a portion of the synthesis gas, the carbon
dioxide gas of which has been separated by the above CO.sub.2
removal unit 20, is also supplied to the hydrogen separator 26. The
hydrogen separator 26 separates the hydrogen gas included in the
synthesis gas, by the adsorption and desorption (hydrogen PSA)
utilizing a pressure difference as described above. This separated
hydrogen is continuously supplied from a gas holder (not shown),
etc. via a compressor (not shown) to various hydrogen-utilizing
reaction devices (for example, the desulfurizing reactor 10, the
wax fraction hydrocracking reactor 50, the middle distillate
hydrotreating reactor 52, the naphtha fraction hydrotreating
reactor 54, etc.) which perform predetermined reactions, utilizing
the hydrogen within the liquid fuel synthesizing system 1.
[0046] Next, the above FT synthesis unit 5 synthesizes liquid
hydrocarbons by the FT synthesis reaction from the synthesis gas
produced by the above synthesis gas production unit 3.
[0047] Specifically, the synthesis gas from which the carbon
dioxide gas has been separated in the above CO.sub.2 removal unit
20 flows in from the bottom of the bubble column reactor 30, and
flows up in the catalyst slurry contained in the bubble column
reactor 30. At this time, within the bubble column reactor 30, the
carbon monoxide gas and hydrogen gas which are included in the
synthesis gas react with each other by the FT synthesis reaction,
thereby producing hydrocarbons. Moreover, by flowing water through
the heat transfer pipe 32 of the bubble column reactor 30 at the
time of this synthesis reaction, the reaction heat of the FT
synthesis reaction is removed, and a portion of the water heated by
this heat exchange is vaporized into a steam. In the steam and
water, the water separated in the vapor-liquid separator 34 is
returned to the heat transfer pipe 32, and a gas component is
supplied to an external device as a medium-pressure steam (for
example, 1.0 to 2.5 MPaG).
[0048] The liquid hydrocarbons synthesized in the bubble column
reactor 30 in this way are drawn from the middle part of the bubble
column reactor 30, and are introduced to the separator 36. The
separator 36 separates the liquid hydrocarbons into a catalyst
(solid component) in the drawn slurry, and a liquid component
including a liquid hydrocarbon product. A portion of the separated
catalyst is returned to the bubble column reactor 30, and the
liquid component is supplied to the first fractionator 40. From the
top of the bubble column reactor 30, an unreacted synthesis gas,
and a gas component of the synthesized hydrocarbons are introduced
into the vapor-liquid separator 38. The vapor-liquid separator 38
cools down these gases to separate some condensed liquid
hydrocarbons to introduce them into the first fractionator 40.
Meanwhile, as for the gas component separated in the vapor-liquid
separator 38, the unreacted synthesis gases (CO and H.sub.2) are
returned to the bottom of the bubble column reactor 30, and are
reused for the FT synthesis reaction. Additionally, the emission
gas (flare gas) which is not a product and which contains, as a
main component, hydrocarbon gas having a small carbon number
(C.sub.4 or less), may be used as fuel gas of the reformer 12, or
may be introduced into an external combustion facility (not shown),
be combusted therein, and then be emitted to the atmosphere.
[0049] Next, the first fractionator 40 heats the liquid
hydrocarbons (the carbon numbers of which are various) supplied via
the separator 36 and the vapor-liquid separator 38 from the bubble
column reactor 30 as described above, to fractionally distill the
liquid hydrocarbons using a difference in boiling points, i.e.,
separates and refines the liquid hydrocarbons into a naphtha
fraction (the boiling point of which is lower than about
150.degree. C.), a kerosene and gas oil fraction (a middle
distillate (the boiling point of which is about 150 to 360.degree.
C.) equivalent to kerosene and gas oil), and a wax fraction (the
boiling point of which is higher than about 360.degree. C.). The
liquid hydrocarbons (mainly C.sub.21 or more) as the wax fraction
drawn from the bottom of the first fractionator 40 are transferred
to the wax fraction hydrocracking reactor 50, the liquid
hydrocarbons (mainly C.sub.11 to C.sub.20) as the middle distillate
equivalent to kerosene and gas oil drawn from the middle part of
the first fractionator 40 are transferred to the middle distillate
hydrotreating reactor 52, and the liquid hydrocarbons (mainly
C.sub.5 to C.sub.10) as the naphtha fraction drawn from the top of
the first fractionator 40 are transferred to the naphtha fraction
hydrotreating reactor 54.
[0050] The wax fraction hydrocracking reactor 50 hydrocracks the
liquid hydrocarbons as the wax fraction with a large carbon number
(approximately C.sub.21 or more), which has been supplied from the
bottom of the first fractionator 40, by using the hydrogen gas
supplied from the above hydrogen separator 26, to reduce the carbon
number to C.sub.20 or less. In this hydrocracking reaction, the wax
fraction is converted into hydrocarbons with a small carbon number
by cleaving C--C bonds of hydrocarbons with a large carbon number,
using a catalyst and heat. A product including the liquid
hydrocarbons hydrocracked in this wax fraction hydrocracking
reactor 50 is separated into a gas and a liquid in the vapor-liquid
separator 56, the liquid hydrocarbons of which are transferred to
the second fractionator 70, and the gas component (including a
hydrogen gas) of which is transferred to the middle distillate
hydrotreating reactor 52 and the naphtha fraction hydrotreating
reactor 54.
[0051] The middle distillate hydrotreating reactor 52 hydrotreats
liquid hydrocarbons (approximately C.sub.11 to C.sub.20) as the
middle distillate equivalent to kerosene and gas oil having a
substantially middle carbon number, which have been supplied from
the middle part of the first fractionator 40, by using the hydrogen
gas supplied via the wax fraction hydrocracking reactor 50 from the
hydrogen separator 26. This hydrotreating reaction is a reaction
which adds hydrogen to unsaturated bonds of the above liquid
hydrocarbons, to saturate the liquid hydrocarbons to produce
saturated hydrocarbons and isomerize linear chain saturated
hydrocarbons. As a result, a product including the hydrotreated
liquid hydrocarbons is separated into a gas and a liquid in the
vapor-liquid separator 58, the liquid hydrocarbons of which are
transferred to the second fractionator 70, and the gas component
(including hydrogen gas) of which is reused for the above
hydrogenation reaction.
[0052] The naphtha fraction hydrotreating reactor 54 hydrotreats
liquid hydrocarbons (approximately C.sub.10 or less) as the naphtha
fraction with a low carbon number, which have been supplied from
the top of the first fractionator 40, by using the hydrogen gas
supplied via the wax fraction hydrocracking reactor 50 from the
hydrogen separator 26. As a result, a product including the
hydrotreated liquid hydrocarbons is separated into a gas and a
liquid in the vapor-liquid separator 60, the liquid hydrocarbons of
which are transferred to the naphtha stabilizer 72, and the gas
component (including a hydrogen gas) of which is reused for the
above hydrogenation reaction.
[0053] Next, the second fractionator 70 distills the liquid
hydrocarbons supplied from the wax fraction hydrocracking reactor
50 and the middle distillate hydrotreating reactor 52 as described
above, thereby fractionally distilling the liquid hydrocarbons into
hydrocarbons (the boiling point of which is lower than about
150.degree. C.) with a carbon number of C.sub.10 or less, kerosene
(the boiling point of which is about 150 to 250.degree. C.), gas
oil (the boiling point of which is about 250 to 360.degree. C.),
and uncracked wax fraction (the boiling point of which is higher
than about 360.degree. C.) from the wax fraction hydrocracking
reactor 50. The uncracked wax fraction is obtained from the bottom
of the second fractionator 70, and this is recycled to the stage
before the wax fraction hydrocracking reactor 50. Kerosene and gas
oil are drawn from the middle part of the second fractionator 70.
Meanwhile, hydrocarbon gases of C.sub.10 or less are drawn from the
top of the second fractionator 70, and are supplied to the naphtha
stabilizer 72.
[0054] Moreover, the naphtha stabilizer 72 distills the
hydrocarbons of C.sub.10 or less, which have been supplied from the
above naphtha fraction hydrotreating reactor 54 and second
fractionator 70, and fractionally distills naphtha (C.sub.5 to
C.sub.10) as a product. Accordingly, a high-purity naphtha is drawn
from the bottom of the naphtha stabilizer 72. Meanwhile, the gas
(flare gas) which is not a product and which contains as a main
component hydrocarbons with a carbon number equal to or lower than
a predetermined number (equal to or lower than C.sub.4), is
discharged from the top of the naphtha stabilizer 72. This gas may
be used as the fuel gas of the reformer 12, may be recovered as LPG
(not shown), and may be introduced into an external fuel facility
(not shown), be combusted therein, and then be emitted to the
atmosphere.
[0055] Next, the catalyst separation system 81 according to the
present invention will be described in detail with reference to
FIG. 2. The catalyst separation system 81 includes the bubble
column reactor 30, the separator 36 which separates the synthesized
liquid hydrocarbons and catalyst slurry, a gas-liquid separator 82
which is provided on the downstream side of the separator 36 to
separate gas hydrocarbons and liquid hydrocarbons from the fluid
including liquid hydrocarbons, which flows out of the separator,
and a receiving tank 83 which first receives the liquid
hydrocarbons and gas hydrocarbons separated by the gas-liquid
separator 82.
[0056] The separator 36 includes a plurality of filters 91 arranged
within the bubble column reactor 30. Ends of branch pipes 92 are
connected to topu of the filters 91, and other ends of these branch
pipes 92 run out to the outside of the reactor 30, and are
connected to a header 94 formed in the shape of a ring. The header
94 is arranged above the filters 91 outside the bubble column
reactor 30, and is arranged so that the center of the ring is made
to coincide with the center of the bubble column reactor 30.
Additionally, the internal diameter D.sub.1 of a pipe of the header
94 is greater than the internal diameter D.sub.2 of the branch
pipes 92.
[0057] The liquid hydrocarbons including gas hydrocarbons filtered
by the filters 91 pass through the branch pipes 92, and are
transferred to the ring-shaped header 94. Here, the liquid
hydrocarbons including gas hydrocarbons are introduced to the
ring-shaped header 94 while being gradually separated into a gas
and a liquid while passing through the branch pipes 92, and are
completely separated into a gas and a liquid in the header.
[0058] In the ring-shaped header 94, one end of a liquid flowing
line 96 through which the liquid hydrocarbons separated inside the
header are transferred, and one end of a gas flowing line 97
through which the gas hydrocarbons separated inside the header are
connected together. That is, the branch pipes 92, the ring-shaped
header 94, the liquid flowing line 96, and the gas flowing line 97
constitute the gas-liquid separator 82. The other ends of the
liquid flowing line 96 and gas flowing line 97 are connected to the
receiving tank 83. The receiving tank 83 is connected to the first
fractionator 40 via a liquid flowing line 98 and a gas flowing line
99.
[0059] Additionally, the branch pipes 92 branch on the way, and are
connected to a tank 101 via communicating pipes 100. A line
including this tank 101 is used to clean the filters 91. When
valves 102 interposed in the communicating pipes 100 and held in a
normally closed state are switched to "open", and valves 103
interposed in the branch pipes 92 and held in a normally opened
state are switched to "close", the fluid stored within the tank 101
in advance flows towards the filters 91, whereby the filters 91 are
cleaned. Such a cleaning method is called a reverse cleaning. Here,
as long as the fluid stored within the tank 101 does not have an
adverse effect on a catalyst, the fluid may be gas or liquid. The
fluid may preferably be liquid (for example, liquid
hydrocarbons).
[0060] Next, the operation of the catalyst separation system 81
will be described.
[0061] From the hydrocarbons synthesized within the bubble column
reactor 30, catalyst slurry is separated by the filters 91 inside
this reactor. The hydrocarbons from which the catalyst slurry has
been separated pass through the branch pipes 92 while including the
gas hydrocarbons. At this time, the hydrocarbons are flowed into
the ring-shaped header 94 while being gradually separated into a
gas and a liquid, and are completely separated into a gas and a
liquid in this ring-shaped header 94.
[0062] Thereafter, the liquid hydrocarbons from which the gas
hydrocarbons have been separated in the header 94 are transferred
to the receiving tank 83 through the liquid flowing line 96.
Further, the gas hydrocarbons separated from the liquid
hydrocarbons in the header 94 are transferred to the receiving tank
83 through the gas flowing line 97. The liquid hydrocarbons and gas
hydrocarbons which have been transferred to the receiving tank 83
exist in a separated manner being almost entirely unmixed within
the receiving tank 83. The liquid hydrocarbons within the receiving
tank 83 are transferred to the first fractionator 40 through the
liquid flowing line 98, and the gas hydrocarbons within the
receiving tank 83 are transferred to the first fractionator 40
through the gas flowing line 99.
[0063] As such, the liquid hydrocarbons including gas hydrocarbons
separated by the filters 91 are separated into liquid hydrocarbons
and gas hydrocarbons by the downstream gas-liquid separator 82, and
are then transferred to the first fractionator 40 separately.
Therefore, compared to a prior case where the hydrocarbons are
transferred in a mixed vapor-liquid phase, volume does not expand
during transfer, and pressure loss within a pipe for transfer can
be minimized. As a result, the flow volume of the hydrocarbons can
be secured as designed.
Second Embodiment
[0064] A second embodiment of a catalyst separation system
according to the present invention will be described referring to
FIG. 3. In addition, for convenience of description, the same
components as those of the first embodiment will be designated by
the same reference numerals, and the description thereof will be
omitted.
[0065] FIG. 3 is a schematic diagram showing the overall
configuration of the catalyst separation system of the second
embodiment of the present invention. In the first embodiment, the
separator 36 that is a filter which separates the synthesized
liquid hydrocarbons and catalyst slurry is an example of a
so-called internal filtration type which is assembled into the
bubble column reactor 30, whereas, in this second embodiment, a
separator 110 that is a filter is an example of a so-called
external filtration type which is arranged outside the bubble
column reactor 30.
[0066] That is, the separator 110 is arranged through the
communicating pipe 111 on the downstream of the bubble column
reactor 30 separately from the bubble column reactor 30.
[0067] The separator 110 includes, for example, a cylindrical
vessel 115, the top and bottom of which are closed, and a plurality
of filters 91 disposed within the vessel 115. The filters 91 are
connected to the endless 94 formed in the shape of a ring via the
branch pipes 92. The header 94 is arranged above the filters 91
outside the vessel 115, and is arranged so that the center of the
ring is made to coincide with the center of the vessel 115. In this
embodiment, the internal diameter D.sub.1 of a pipe of the header
94 is greater than the internal diameter D.sub.2 of the branch
pipes 92.
[0068] In this second embodiment, similarly to the first
embodiment, the liquid hydrocarbons containing gas hydrocarbons
separated by the filters 91 are separated into liquid hydrocarbons
and gas hydrocarbons by the downstream gas-liquid separator 82, and
are then transferred to the first fractionator 40 separately.
Therefore, pressure loss within a pipe for a transfer can be
minimized, and the flow volume of the hydrocarbons can be secured
as designed.
[0069] Although the first and second embodiments of the present
invention have been described hitherto in detail with reference to
the drawings, concrete configurations are not limited to the
embodiments, and the present invention also includes changes or the
like in configuration without departing from the scope and spirit
of the invention.
[0070] For example, in the above first and second embodiments, the
ring-shaped header 94 is provided above and outside the vessel 30
or 115; however, this ring-shaped header 94 does not necessarily
need to be arranged above and outside the vessel. For example, the
header may be arranged below the vessel and may be arranged at a
side of the vessel 30 or 115. Additionally, the header 94 is not
limited to have a ring shape. For example, the header may have a
cylindrical shape, a rectangular parallelepiped shape, or a cubical
shape. In short, it is only necessary for the header to have the
shape and internal capacity such that the liquid hydrocarbons
including gas separated by the filters can be separated into a gas
and a liquid, or separated hydrocarbons can be held as they
are.
[0071] Additionally, although the example of the internal
filtration type and the example of the external filtration type
have been given and described in the first embodiment and the
second embodiment, respectively, it is also possible to use them
together.
INDUSTRIAL APPLICABILITY
[0072] The present invention relates to a catalyst separation
system including a reactor where hydrocarbons are synthesized by a
chemical reaction of a synthesis gas including carbon monoxide gas
and hydrogen gas as main components, and a catalyst slurry having
solid catalyst particles suspended in a liquid, filters which
separate the hydrocarbons and the catalyst slurry, and a gas-liquid
separator which separates the liquid hydrocarbons flowing out of
the filters into gas hydrocarbons and liquid hydrocarbons.
[0073] According to the present invention, it is possible to
minimize pressure loss, thereby securing a predetermined flow
volume, when liquid hydrocarbons synthesized by the FT synthesis
reaction are separated from catalyst slurry and transferred
downstream.
REFERENCE SIGNS LIST
[0074] 30: BUBBLE COLUMN REACTOR (REACTOR) [0075] 36: SEPARATOR
(FILTER) [0076] 81: CATALYST SEPARATION SYSTEM [0077] 82:
GAS-LIQUID SEPARATOR [0078] 83: RECEIVING TANK [0079] 91: FILTER
[0080] 92: BRANCH PIPE [0081] 94: RING-SHAPED HEADER (COLLECTING
PIPE) [0082] 96: LIQUID FLOWING LINE [0083] 97: GAS FLOWING
LINE
* * * * *